On Jul 7, 10:38 am, Ondrej Certik <[email protected]> wrote:
> On Sat, Jul 4, 2009 at 6:52 PM, smichr<[email protected]> wrote:
>
> > I noticed that fastlog in evalf computes an approximation to log2(x).
> > Is there any reason not to call it fastlog2?
>
> Could you please be more specific? Which commands do you mean exactly?
>
Maybe I'm not understanding the confusion, but I mean the fastlog
method in evalf:
###
>>> from sympy import *
>>> evalf.fastlog((0, 1, 2, 1)) #i.e. log(2**2)/log(2) = 2
2
###
Since fastlog is computing the log2 approximation it makes sense to me
to call it fastlog2 rather than fastlog.
There is no test for this function. I've remedied that and also
corrected the function to compute the power of an exact power of 2
properly; previously it was off by 1 in the result. Since the mantissa
of all mpf numbers provided by mpf is suppose to be odd (according to
the documentation) then when the number is an exact power of 2, the
mantissa will be 1, the bitcount of it will also be 1 and the
approximation (exponent + bitcount) is off by 1: the bitcount should
not be added in this case.
If I can figure out how to push my changes to git I will send the
patch for this by that means. For now, I didn't change the name, I
only corrected the function and added tests.
/c
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